It has been well known in the closure art to use molded plastic covers or lids having various types of tear strips to permit easy opening or removal of the cover or lid. The tear strip is integrally molded with the lid having a frangible wall portion interconnecting the tear strip to the main portion of the lid. The tear strips may perform the dual functions of (1) providing a positive indication that the contents of the container have not been distributed or tampered with, and (2) securing the lid in sealed engagement with the container.
The present invention is particularly directed to large plastic lids of the kind used to seal five gallon containers, although it may be made smaller and used for smaller containers. These large containers and lids must often meet a drop test in which the container full of liquid is dropped four feet to see if the lid remains sealed after the drop.
Conventional, large size lids are available that readily pass this drop test but they suffer from not being easily removed from the container. These conventional lids typically have about eight depending skirt segments, each of which has an opening or slot to receive a pointed tool such as a screw driver tip that is driven into the skirt segment; and then the screw driver is used as a lever to pry the segments outwardly to pull their internal sealing bead sections outwardly from the mating sealing bead on the container. A pliers also may be used to grip a skirt segment and used to bend and pull the flange segment radially outwardly. For five gallon paint containers, the plastic usually used is high density polyethylene, which is much less flexible than low density polyethylene and has a cross-sectional thickness such that it often requires considerable force and energy to open such a large lid even after pulling the flange sections outwardly because they are still biased to engage the container locking bead.
Such molded plastic paint containers are often as large as 12 inches in diameter, providing a substantial linear distance over which the seal between lid and container must be maintained. Two limiting aspects to the means of sealing such lids to a container are that the lid must be readily removable without special tools and that the lid must be removable in a manner that does not destroy the capacity of the lid to be reused. As explained above, the lid should be removable with the aid of a pair of pliers and a screw driver, and should be in a form that may be re-applied to the container to again reclose the container. Also, such lids must be capable of being molded on high speed injecting molding equipment to be economically competitive with similarly molded plastic lids.
One attempt to make such lids easier to open involves the use of a tear strip which removes parts of the sealing flange on a plastic lid. Such a lid construction is disclosed in the U.S. Patent to Von Holdt U.S. Pat. No. 4,735,337. The plastic lid of the embodiment of FIG. 1 of the Von Holdt Patent has a peripheral flange that is formed with an inwardly extending annular gripping projection that engages the container and includes a tear strip that is formed by an internal V-groove on the inside of the skirt hidden from the user's view. Pulling the tear strip from the skirt removes peripherally spaced portions of the gripping projection to lessen the gripping force provided by the flange. After removing the tear strip and the spaced portions of the gripping projection, the remaining flange portions may be deflected outwardly to permit easier removal of the lid. This removal requires the simultaneous outward deflection of these remaining flange portions, while at the same time lifting up on the lid. The outward deflection must be sufficient to disengage the gripping projection from the annular bead or shoulder provided on the outer periphery of the upper edge of the container wall.
Upon reuse of the above described lid of the '337 patent, the lid is forced back on to the container with sufficient force to deflect the remaining flange portions outwardly whereby the gripping projections may re-engage with the underside of the shoulder or bead on the container.
The '337 patent discloses a second embodiment in FIGS. 5 to 7 which utilizes no tear strip and no removable portion on the lid flange 5, but instead has frangible connections between the peripherally spaced flange portions. Once the frangible connections have been severed between the flange portions, a number of peripherally spaced flange portions may be folded upwardly where they tend to remain with their gripping projections disengaged from the container. The lid may then be removed by deflecting the remaining flange portions outwardly in the same manner as with the embodiment of FIGS. 1-4 Thus, the flange portions must be flexed outwardly at the same time the lid is urged upwardly.
In reclosing a container using the lid of the FIGS. 5-7 embodiment of the '337 patent, the same problem as discussed in connection with the FIGS. 1-4 embodiment is encountered. A sufficient force must be applied to the lid to deflect the flange portions from their downwardly disposed position to the outwardly deflected position so that the gripping projections may pass over the annular bead on the container and re-engage with the underside of the bead. After these flange portions have been re-engaged, the intermediate flange portions that were folded outwardly may then be folded downwardly to their re-engaged positions.